Process for the preparation of metallic screens for luminous projections



Patented that. 13, 192.55,.

K Y PIERRE JEAN JlIABTIN,

0E BRUSS L BELGIUM.

PROCESS FOR THE IPREPARATION O1? METALLIG FDR LUMIINO'US PROJEGTiONS.

No Drawing.

To all whom it may con 0mm:

Be it known that I, PIERRE JEAN lilnnrm, citizen of the United States of America, residing at Brussels, in the Kingdom of Belgiuni, have invented certain new and useful Improvements in Processes for the Preparation of Metallic Screens for Luminous Projections, of which the following is a specification.

The present invention relates to a process for the preparation of screens generally used for cinematographic and other luminous projections, its object being to improve the production of what are generally termed metallized screens.

It is known that in the metalization process the application of the metallizing sub stance to the plain coating serving as a backing and forming the background of the screen, produces a smooth reductive surface, but in the more illuminated parts of the project-ion reflections and halos result from this smoothness. It is necessary to minimize this effect to secure the sharp definition of the images projected and the natural means of obtaining this attenuation is to break up the bundles of lightrays reflected by the screen, by imparting to the latter diffusing qualities to disperse the rays received and thus to suppress the reflections. With this object in view it has been proposed to apply a metallizing coat consisting of a mixture of gold size, aluminium powder and silver powder and when this coating is dry to dust it with a mixture of aluminium powder and silver powder in a dry state. It has also been proposed to provide a metallized screen, obtained by the application of silver, bronze or other metal, with indentations or striations so as to provide a surface broken up by a large number of projections and recesses. The application of a sand-blast has given the desired effect in some instances whilst in other instancesthe effect has been obtained by etching or special shaping.

According to the present invention the background coating has added to it a coating of fine grains offiint, or other such material constituting an infinity of small asperities, the cracks or fissures of which are filled by a special metallizing substance applied subsequently, and which reflect in all directions due to their multiple orientations the light which they receive and diffuse it without reducing any of its intensity. The application of grains of flint must not be Application filed July 24;,

1923. Serial No. 653,616.

confused with sand-blasting wherein the particles of sand after impinging; on the screen to create a number of indentations fall away as usual and therefore do not form part of the surface. j j

As to the special metallizinp; substance re ferred to, aluminium the chief constituout but while theuse of this metal has found favor in the art by reason of its natural qualities and of its relatively satisfactory brilliancy, yet it has the drawback of quickly tarnishing and thus rapidly losing its refleeting qualities. The substitution for aluminium of another metal, better able to withstand oxidation but necessarily of a higher density, would constitute a grave drawback for screens of large dimensions. It is therefore essential, whilst retaining the advantages of the use of, aluminium, to lengthen the effective life of the screen by a suitable preparation of the metallizing substance capable of increasing its brilliancy and correspondingly reducing the energy consumed by the illuminating source. For this purpose, according to my invention, there is incorporated with the aluminium a very small proportion fgold in the pure state. ()wing to the extreme ductility of gold it is possible to obtain a considerable surface in relation to the volume used and it has been found that by distributing it in'the aluminium the intensity of the brilliancy of the metallizing; coating is increased to avery large extent.

The gold beaten into extremely thin sheets is, prior to its incorporation with aluminium divided into minute facets of sizes corresponding to the degree of fineness of the grains of flint covering the screen, in such wise that the sum total of the surfaces re sulting from this division may not be less than the original surface of the sheets from which they are made. The particles of gold are uniformly distributed in the aluminuim and the multiple facets thus produced are, at the time of the metalization, applied to the asperities of the flint, giving the full brilliancy due to the polish of each of them whilst preserving, by their orientation in all directions, the entirety of the diffusing effect desired. For the same reasons and for the same object a similar treatment is applied to a part of the aluminium used, that is to say it is divided up into minute facets from very thin sheets, the other part, intended 0 Serve as connecting m d ate leetwe n e Cir different 'facetfs"offinetal, being; utilized in the form of powder and only-constituting, practically speaking, the background of the inetallized surface. .s r

In a screen produced by the process accordingtoth'is invention;a1though thenletallized surface will consist largely of aluminium the drawbacks referred to "are avoiiiedb the incorporation of ,the precious metal "which yielding for asinallyolume proportionately considerable surfaces uniformly distributed over the netallized surface, covers an appreciable part *of the rn'etalliz'ed surface, each of, the metal particlesincorpoi-at aprervin the 'iyhole'of the reflecting "qualiti-ifs and these qualities being enhanced partial are resented.

ducing m talhzed screens for f cinematographic and other projections, Wh1cl1 consists 1n applying a coating of fine grains 'offlinttoaplain backing and applying to said coating a lnetallizing layer consisting of aluminium admixed With a small "proportion of gold in the pure state finely divided from thin sheets into minute facet's df "digiven increased brillianoy.

2. Inthe herein described processof producing lnetallized screens, in combination ii'itlrthe steps claimed in claim 1, the step ofiinely 'coiiiihinuting the alulniniulil prior to its admixture With the gold. V

In testinion'y whereof I aflix ny'si gnature.

PIERRE JEAN MARTIN. 

